1. Technical Field
The present disclosure relates to a wiring substrate including an insulating film for covering an upper surface and a lower surface of a semiconductor substrate, a first wiring pattern disposed on an upper surface side of the semiconductor substrate and coupled to a through electrode and an electronic component, and a second wiring pattern disposed on a lower surface side of the semiconductor substrate and coupled to the through electrode and a mounting substrate.
2. Related Art
In the related art, as the wiring substrate (interposer) for connecting electrically the semiconductor chip and the mounting substrate such as the motherboard, a wiring substrate 200 shown in FIG. 1 is used.
FIG. 1 is a sectional view of a wiring substrate in the related art.
By reference to FIG. 1, the wiring substrate 200 includes a semiconductor substrate 206 as a base material, an insulating film 207, through electrodes 208, and first and second wirings 211, 212.
The semiconductor substrate 206 is a substrate shaped like a plate, and has through holes 215. As the semiconductor substrate 206, for example, a silicon substrate can be used. The insulating film 207 is formed to cover an upper surface 206A and a lower surface 206B of the semiconductor substrate 206 and surfaces of the semiconductor substrate 206, which are exposed from the through holes 215. A dielectric constant of the insulating film 207 is larger than a dielectric constant 1.0 of the air and is about 3.8.
The through electrodes 208 are provided in the through holes 215 on which the insulating film 207 is formed. The through electrodes 208 are used to connect electrically the first wiring 211 and the second wiring 212. As the material of the through electrodes 208, for example, Cu can be used.
The first wiring 211 is provided to extend over the insulating film 207 that is formed from upper end portions of the through electrodes 208 to the upper surface 206A of the semiconductor substrate 206. The first wiring 211 is a wiring to which an electronic component 201 is connected (mounted). As the electronic component 201, the semiconductor chip whose base material is formed of the silicon substrate can be used.
The second wiring 212 is provided to extend over the lower surface of the insulating film 207 that is formed from lower end portions of the through electrodes 208 to the lower surface 206B of the semiconductor substrate 206. The second wiring 212 is a wiring that is connected electrically to pads 203 of a mounting substrate 202 (concretely, the mother board, for example). As the material of the base member of the mounting substrate 202, a resin can be used (see e.g., JP-A-2007-42741).
However, in the wiring substrate 200 in the related art, the first and second wirings 211, 212 contact the insulating film 207. Therefore, there is a problem that a transmission speed of a signal transmitted between the electronic component 201 connected to the first wiring 211 and the mounting substrate 202 connected electrically to the second wiring 212 cannot be increased.
Also, a material of the base member (concretely, silicon) of the wiring substrate 200 is different from that of the base member (concretely, resin) of the mounting substrate 202. Therefore, there is a problem that reliability of electrical connection between the wiring substrate 200 and the mounting substrate 202 is decreased on account of a difference of coefficient of thermal expansion between the wiring substrate 200 and the mounting substrate 202.